The South-to-North Water Diversion (SNWD) Project is the largest inter basin water transfer project in the world. Danjiangkou Reservoir is water source of Middle Route Project of the South-to-North Water Diversion Project. Since the water was opened in December 2014, the problem of water shortage in northern China has been greatly alleviated. However, some studies have shown that the SNWD Project greatly reduces the available water resources in the downstream of the reservoir and affects the vegetation growth and agricultural production in the downstream and upstream. On the other hand, the problems of permanent land occupation, water storage and resettlement caused by the SNWD Project have caused many ecological and environmental problems in the reservoir area, and have a profound impact on the whole basin. It is of great value to evaluate the changes of ecological environment in the basin under the SNWD Project, which is of great value for guiding the ecological construction and development of the basin and scientific water transfer, and also provides a reference for the scientific identification of the basin ecological environment response mechanism under the influence of large-scale water conservancy projects. At present, before and after the Middle Route Project of SNWD Project, the quantitative research on the change characteristics and response law of the overall ecological environment in Danjiangkou reservoir area is lack. Therefore, this study takes Danjiangkou reservoir and Han River Basin as the research object, calculates and analyzes the spatial-temporal dynamic changes of reservoir water volume, watershed vegetation and ecosystem services value before and after water diversion, explores the influence of water volume on the changes of vegetation and ecosystem services value, with the help of land use, climate, socio-economic data to understand the driving forces of vegetation and ecosystem services value change, quantitatively evaluate the impact of SNWD Project on the ecological environment of the river basin, and scientifically identify the ecological environment of the river basin from the two aspects of basic data support and theoretical basis. The response characteristics of the basin ecological environment to the SNWD Project are scientifically identified, which lays the foundation for improving the incentive system of ecological environment protection.